Pain Is Modulated Differently Between Females with and without Patellofemoral Pain: Factors Related to Sensitization.

CONTEXT: Patellofemoral pain (PFP) has poor long-term recovery outcomes. Central sensitization describes central nervous system changes altering pain modulation, which can complicate recovery (poorer prognosis, worse function). Signs of central sensitization include amplified pain facilitation, pain hypersensitivity, and impaired pain inhibition, which can be measured with temporal summation of pain (TSP), pressure pain thresholds (PPTs) and conditioned pain modulation (CPM), respectively. Sex differences exist for these test responses, but female-only PFP investigations of sensitization are uncommon. Understanding pain modulation in females with PFP could improve treatment protocols. OBJECTIVE: To determine whether females with PFP exhibit signs of central sensitization (greater TSP, lower PPTs, reduced CPM) compared to pain-free females. DESIGN: Cross-sectional Setting: Laboratory Patients or Other Participants: Thirty-three females [(20 PFP, 13 pain-free); Age: PFP 29.2 ± 7 years, pain-free 28 ± 7 years; Height: PFP 166.7 ± 5.9cm, pain-free 166 ± 9.5cm, Mass: PFP 66.7 ± 9.6kg, pain-free 69.3 ± 7.5kg). MAIN OUTCOME MEASURES: TSP was assessed with ten punctate stimuli applied to the knee and calculated by the difference in pain intensity between beginning and end responses. PPTs were tested at four sites [3 for local hypersensitivity (knee), 1 for widespread hypersensitivity (hand)]. CPM was conducted by comparing PPTs during two conditions (baseline, ice immersion). CPM response was defined as the percent difference between conditions. Between-group differences in TSP response were analyzed with a Welch's test. Separate Welch's tests analyzed group comparisons of PPTs and CPM responses at four sites. RESULTS: Females with PFP exhibited greater TSP response (P=0.019) and lower CPM response at patella center (P=0.010) and hand sites (P=0.007) than pain-free females. PPT group differences were not observed at any site (P>0.0125). CONCLUSIONS: Females with PFP modulate pain differently than pain-free females. Clinicians should recognize signs of central sensitization and their potential impact on treatment options.

Visual feedback and declines in attention are associated with altered visual strategy during a force-steadiness task in older adults.

Greater heterogeneity exists in older adults relative to young adults when performing highly skilled manual tasks. The purpose of this study was to assess the influence of visual feedback and attentional demand on visual strategy during a submaximal force-steadiness task in young and older adults. Eye movements of 21 young (age 20-38 yr; 11 females, 10 males) and 21 older (age 65-90 yr; 11 females, 10 males) adults were recorded during a pinch force-steadiness task while viewing feedback with higher and lower gain and while performing a visuospatial task. For the visuospatial task, participants imagined a star moving around four boxes and reported the final location after a series of directions. Performance on standardized tests of attention was measured. All participants gazed near the target line and made left-to-right saccadic eye movements during the force-steadiness tasks without the visuospatial task. Older adults made fewer saccades than young adults (21.0 ± 2.9 and 23.6 ± 4.4 saccades, respectively) and with higher versus lower gain (20.9 ± 4.0 and 23.7 ± 3.5 saccades, respectively). Most participants used the same visual strategy when performing the visuospatial task though seven older adults used an altered strategy; gaze did not stay near the target line nor travel exclusively left to right. Performance on standardized measures of attention was impaired in this subset compared with older adults who did not use the altered visual strategy. Results indicate that visual feedback influences visual strategy and reveals unique eye movements in some older adults when allocating attention across tasks.NEW & NOTEWORTHY This study contributes novel findings of age-related changes in visual strategy and associations with attentional deficits during hand motor tasks. Older adults used fewer saccades than young adults and with higher versus lower gain visual feedback during a force-steadiness task. A subset of older adults used an altered visual strategy when allocating attention across multiple tasks. Given that this subset demonstrated attentional deficits, the altered visual strategy could serve to indicate motor and/or cognitive impairments.

Lived experiences of American adults who survive COVID-19: Implications for physical activity and interpersonal stress.

INTRODUCTION: The cumulative number of COVID-19 cases has surpassed 579 million globally. Symptoms during and after COVID-19 infection vary from mild cold symptoms to severe multisystem illness. Given the wide range of symptom presentations and complications post-COVID-19, the purpose of this study was to describe the lived experience of American adults surviving COVID-19. METHOD: This study employed an exploratory qualitative description design. Semi-structured interviews were conducted with a sample of 35 individuals (White [94%], female [71%], Mage = 43.7 years), with proximity to a university in an urban Midwest American city. Interviews occurred between May and August 2021, 3 or more months after participants tested positive for COVID-19. RESULTS: Forty percent of the 35 participants experienced prolonged COVID-19 symptoms impacting their lifestyle. Four themes characterized the impacts of the post-COVID-19 condition on the lives of the participants within the context of a global pandemic: (a) disruptions in health and well-being, (b) persistent uncertainty, (c) disruptions in interpersonal relationships, (d) beneficent outcomes and adaptation. DISCUSSION: This study of COVID-19 has identified important implications for physical activity and interpersonal stress. Prolonged COVID-19 symptoms led to disruptions in the health, well-being, and interpersonal relationships of participants. Health care professionals need to attend to symptoms post-COVID-19, assess interpersonal functioning, and provide guidance on physical activity. Future studies are recommended to track consequences of COVID-19's impact on long-term health and well-being. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Health sciences students' career commitment, mental health, and physical activity during the COVID-19 pandemic.

Objective: To understand the biopsychosocial dimensions of university health sciences students' experiences during the COVID-19 pandemic. Participants: Health sciences students (n = 297) from two universities in July and August 2020. Methods: Participants completed a Web-based survey asking about depression, anxiety, physical activity, coronavirus threat, and career commitment. Results: Moderate or severe depression and anxiety were reported by 28.6% and 31.3% of respondents, respectively. Depression and anxiety were positively correlated with perceived coronavirus threat and negatively correlated with career commitment and strenuous physical activity. A change in career commitment interests during the COVID-19 pandemic was reported by 11% of respondents. Conclusions: Identified factors that could be targeted by universities to support their students and secure career commitment include online learning challenges, ability to secure clinical placements, mental health (anxiety and depression), financial challenges, family pressure, and promotion of physical activity.

Impaired conditioned pain modulation was restored after a single exercise session in individuals with and without fibromyalgia.

Introduction: Exercise is an effective nonpharmacological intervention for individuals with fibromyalgia syndrome (FMS); however, considerable variability is observed in their pain response after a single exercise session that could be due to differences in baseline central pain inhibition (ie, conditioned pain modulation [CPM]). Objectives: This study examined the effect of isometric exercise on CPM in people with FMS and control participants. A subaim was to identify whether pain inhibition after exercise was due to differences in baseline CPM. Methods: Twenty-one individuals with FMS (50.5 ± 14.9 years) and 22 age-matched and sex-matched controls (49.2 ± 13.3 years) participated in a familiarization session and 2 randomized experimental sessions: (1) low-intensity isometric exercise and (2) quiet rest control. Conditioned pain modulation was measured before and after each experimental session. In addition, body composition and physical activity levels were collected to determine potential group differences. Results: Both groups had comparable body composition and physical activity levels and reported similar exercise-induced hypoalgesia (increase in pressure pain thresholds) at the exercising muscle (quadriceps muscle) and systemically (deltoid muscle). Both groups had a decrease in CPM after exercise and quiet rest; however, in both FMS and control participants with impaired baseline CPM, there was an increase in CPM at the deltoid muscle after exercise. Conclusion: In persons with low CPM, irrespective of health status, isometric exercise enhanced CPM at a site distal from the exercising muscle. Our results support the use of isometric exercise when initiating an exercise program especially for individuals with impaired CPM.

The role of eye movements, attention, and hand movements on age-related differences in pegboard tests.

Well-documented manual dexterity impairments in older adults may critically depend on the processing of visual information. The purpose of this study was to determine age-related changes in eye and hand movements during commonly used pegboard tests and the association with manual dexterity impairments in older adults. The relationship between attentional deficits and manual dexterity was also assessed. Eye movements and hand kinematics of 20 young (20-38 yr) and 20 older (65-85 yr) adults were recorded during 9-Hole Pegboard, Grooved Pegboard, and a visuospatial dual test. Results were compared with standardized tests of attention (The Test of Everyday Attention and Trail Making Test) that assess visual selective attention, sustained attention, attentional switching, and divided attention. Hand movement variability was 34% greater in older versus young adults when placing the pegs into the pegboard and this was associated with decreased pegboard performance, providing further evidence that increased movement variability plays a role in dexterity impairments in older adults. Older adults made more corrective saccades and spent less time gazing at the pegboard than young adults, suggesting altered visual strategies in older compared with young adults. The relationship between pegboard completion time and Trail Making Test B demonstrates an association between attentional deficits and age-related pegboard impairments. Results contribute novel findings of age-associated changes in eye movements during a commonly used manual dexterity task and offer insight into potential mechanisms underlying hand motor impairments in older adults.NEW & NOTEWORTHY This eye tracking study contributes novel findings of age-associated changes in eye movements during the commonly used pegboard tests of manual dexterity, including a greater number of corrective saccades and lesser time gazing at the pegboard holes in older compared with young adults. An association between attentional deficits and dexterity impairments in older adults is also highlighted. Results shed light on potential mechanisms underlying well-documented motor deficits in older adults.

Temporal aspects of endogenous pain modulation during a noxious stimulus prolonged for 1 day.

BACKGROUND: This study investigated (a) if a prolonged noxious stimulus (24-hr topical capsaicin) in healthy adults would impair central pain inhibitory and facilitatory systems measured as a reduction in conditioned pain modulation (CPM) and enhancement of temporal summation of pain (TSP) and (b) if acute pain relief or exacerbation (cooling and heating the capsaicin patch) during the prolonged noxious stimulus would affect central pain modulation. METHODS: Twenty-eight participants (26.2 ± 1.0 years; 12 women) wore a transdermal 8% capsaicin patch on the forearm for 24 hr. Data were collected at baseline (Day 0), 1 hr, 3 hr, Day 1 (post-capsaicin application) and Day 3/4 (post-capsaicin removal) that included capsaicin-evoked pain intensity, heat pain thresholds (HPTs), TSP (10 painful cuff pressure stimuli on leg) and CPM (cuff pressure pain threshold on the leg prior vs. during painful cuff pressure conditioning on contralateral leg). After 3 hr, cold (12°C) and heat (42°C) stimuli were applied to the capsaicin patch to transiently increase and decrease pain intensity. RESULTS: Participants reported moderate pain scores at 1 hr (2.5 ± 2.0), 3 hr (3.7 ± 2.4), and Day 1 (2.4 ± 1.8). CPM decreased 3-hr post-capsaicin (p = .001) compared to Day 0 and remained diminished while the capsaicin pain score was reduced (0.4 ± 0.7, p < .001) and increased (6.6 ± 2.2, p < .001) by patch cooling and heating. No significant differences occurred for CPM during patch cooling or heating compared to initial 3HR; however, CPM during patch heating was reduced compared with patch cooling (p = .01). TSP and HPT did not change. CONCLUSIONS: This prolonged experimental pain model is useful to provide insight into subacute pain conditions and may provide insight into the transition from acute to chronic pain. SIGNIFICANCE: During the early hours of a prolonged noxious stimulus in healthy adults, CPM efficacy was reduced and did not recover by temporarily removing the ongoing pain indicating a less dynamic neuroplastic process.

Fatiguing Trunk Flexor Exercise Decreases Pain Sensitivity in Postpartum Women.

BACKGROUND: Low back pain (LBP) is common in the general population and among postpartum women. Abdominal muscle exercise is often used to treat LBP, but it is unknown if fatiguing abdominal muscle exercise can produce exercise-induced hypoalgesia (EIH). OBJECTIVES: To assess pressure pain thresholds (PPTs) at rest and following fatiguing trunk flexor exercise (EIH) in (1) nulligravid and postpartum women to evaluate the impact of pregnancy and childbirth and (2) nulligravid women and men to examine sex differences. METHODS: Seventy healthy adults (31 postpartum women, 23 nulligravid women, 16 men) participated. Postpartum and nulligravid women were tested twice (16-18 weeks apart) to identify changes in EIH with postpartum recovery. PPTs were measured at the nailbed and superior rectus abdominis before and after exercise to investigate systemic and local EIH, respectively. Rectus abdominis muscle thickness was assessed with ultrasound. RESULTS: Postpartum women reported lower PPTs than nulligravid women at the abdomen (p < 0.05) whereas postpartum women had lower PPTs at the nailbed during the first session only. Men reported higher nailbed PPTs (p = 0.047) and similar PPTs at the abdomen than women (p = 0.294). All groups demonstrated EIH at the abdomen (p < 0.05). Systemic EIH was absent in postpartum and nulligravid women (p > 0.05), while men demonstrated hyperalgesia. Local EIH was positively associated with muscle thickness for men and women, which was not significant at the second timepoint. LIMITATIONS: Acute exercise response may not reflect changes that occur with exercise training. CONCLUSION: Fatiguing trunk flexor exercise produced local EIH for all groups including postpartum and nulligravid women. Clinically, trunk exercises may be useful for acute pain relief for clinical populations that are characterized by pain and/or weakness in the abdominal region muscles in populations with abdominal pain syndromes.

Does Weight Status Impact Metabolic Health in Adolescents When Controlling for Physical Fitness?

PURPOSE: To determines whether adolescents who are fit with overweight/obesity are similar in their metabolic profile to adolescents who are fit and normal weight. METHODS: Adolescents participated in 3 sessions: (1) resting vitals and anthropometrics; (2) maximal aerobic treadmill test ((Equation is included in full-text article.)) to determine physical fitness; and (3) dual-energy x-ray absorptiometry and fasting laboratory draw for analysis of insulin, glucose, high-density lipoprotein, triglycerides, and C-reactive protein. RESULTS: Of the 30 fit adolescents who are normal weight and 16 adolescents who are fit and overweight/obese (OW/OB), metabolic syndrome was apparent in 1 adolescent who are normal weight and 4 adolescents who are OW/OB. Metabolic syndrome severity was positively associated with body mass index, waist circumference, total body fat, insulin resistance, and C-reactive protein but inversely associated with peak relative, but not lean (Equation is included in full-text article.). CONCLUSIONS: Despite good physical fitness, adolescents who are OW/OB demonstrated greater metabolic syndrome than adolescents who are normal weight. Future intervention research is necessary to explore the relation between physical fitness and metabolic syndrome.

Systemic Exercise-Induced Hypoalgesia Following Isometric Exercise Reduces Conditioned Pain Modulation.

Objective: Physically active individuals show greater conditioned pain modulation (CPM) compared with less active individuals. Understanding the effects of acute exercise on CPM may allow for a more targeted use of exercise in the management of pain. This study investigated the effects of acute isometric exercise on CPM. In addition, the between-session and within-session reliability of CPM was investigated. Design: Experimental, randomized crossover study. Setting: Laboratory at Marquette University. Subjects: Thirty healthy adults (19.3±1.5 years, 15 males). Methods: Subjects underwent CPM testing before and after isometric exercise (knee extension, 30% maximum voluntary contraction for three minutes) and quiet rest in two separate experimental sessions. Pressure pain thresholds (PPTs) at the quadriceps and upper trapezius muscles were assessed before, during, and after ice water immersions. Results: PPTs increased during ice water immersion (i.e., CPM), and quadriceps PPT increased after exercise (P < 0.05). CPM decreased similarly following exercise and quiet rest (P > 0.05). CPM within-session reliability was fair to good (intraclass correlation coefficient [ICC] = 0.43-0.70), and the between-session reliability was poor (ICC = 0.20-0.35). Due to the variability in the systemic exercise-induced hypoalgesia (EIH) response, participants were divided into systemic EIH responders (N = 9) and nonresponders (N = 21). EIH responders experienced attenuated CPM following exercise (P = 0.03), whereas the nonresponders showed no significant change (P > 0.05). Conclusions: Isometric exercise decreased CPM in individuals who reported systemic EIH, suggesting activation of shared mechanisms between CPM and systemic EIH responses. These results may improve the understanding of increased pain after exercise in patients with chronic pain and potentially attenuated CPM.

Lean mass mediates the relation between temporal summation of pain and sex in young healthy adults.

BACKGROUND: Previous studies have shown that women experience greater temporal summation (TS) of pain than men using a repetitive thermal stimulus. These studies, however, did not individualize the thermal stimulus to each subject's thermal pain sensitivity. The aim of this study was to investigate sex differences in TS using an individualized protocol and potential mediators that have been shown to influence TS including physical activity and body composition. METHODS: Fifty young healthy men and women (21 men) participated in the study. Subjects completed TS testing on the right forearm using a repetitive thermal stimulus at a temperature that the subject reported 6/10 pain. Other testing included body composition (lunar iDXA), activity monitoring (Actigraph), and Pain Catastrophizing Scale (PCS). RESULTS: Women reported greater TS than men (p = 0.019), and TS was correlated with right arm lean mass (r = - 0.36, p = 0.01) and magnification subscale of PCS (r = - 0.32, p = 0.03). Mediation analysis showed a complete mediation for the relation between sex and TS by right arm lean mass (indirect effect = 2.33, 95% BCa CI [0.42, 4.58]) after controlling for the temperature, the magnification subscale of PCS, and the average time spent in moderate to vigorous physical activity. CONCLUSION: The results of this study suggest that lean mass is a contributing factor to the sex differences in TS. Future studies should investigate whether interventions that increase lean mass have a positive effect on TS.

Sex Differences in Arm Muscle Fatigability With Cognitive Demand in Older Adults.

BACKGROUND: Muscle fatigability can increase when a stressful, cognitively demanding task is imposed during a low-force fatiguing contraction with the arm muscles, especially in women. Whether this occurs among older adults (>60 years) is currently unknown. QUESTIONS/PURPOSES: We aimed to determine if higher cognitive demands, stratified by sex, increased fatigability in older adults (>60 years). Secondarily, we assessed if varying cognitive demand resulted in decreased steadiness and was explained by anxiety or cortisol levels. METHODS: Seventeen older women (70±6 years) and 13 older men (71±5 years) performed a sustained, isometric, fatiguing contraction at 20% of maximal voluntary contraction until task failure during three sessions: high cognitive demand (high CD=mental subtraction by 13); low cognitive demand (low CD=mental subtraction by 1); and control (no subtraction). RESULTS: Fatigability was greater when high and low CD were performed during the fatiguing contraction for the women but not for the men. In women, time to failure with high CD was 16±8 minutes and with low CD was 17±4 minutes, both of which were shorter than time to failure in control contractions (21±7 minutes; high CD mean difference: 5 minutes [95% confidence interval {CI}, 0.78-9.89], p=0.02; low CD mean difference: 4 minutes [95% CI, 0.57-7.31], p=0.03). However, in men, no differences were detected in time to failure with cognitive demand (control: 13±5 minutes; high CD mean difference: -0.09 minutes [95% CI, -2.8 to 2.7], p=1.00; low CD mean difference: 0.75 minutes [95% CI, -1.1 to 2.6], p=0.85). Steadiness decreased (force fluctuations increased) more during high CD than control. Elevated anxiety, mean arterial pressure, and salivary cortisol levels in both men and women did not explain the greater fatigability during high CD. CONCLUSIONS: Older women but not men showed marked increases in fatigability when low or high CD was imposed during sustained static contractions with the elbow flexor muscles and contrasts with previous findings for the lower limb. Steadiness decreased in both sexes when high CD was imposed. CLINICAL RELEVANCE: Older women are susceptible to greater fatigability of the upper limb with heightened mental activity during sustained postural contractions, which are the foundation of many work-related tasks.

The current state of physical therapy pain curricula in the United States: a faculty survey.

UNLABELLED: Insufficient pain education is problematic across the health care spectrum. Recent educational advancements have been made to combat the deficits in pain education to ensure that health care professionals are proficient in assessing and managing pain. The purpose of this survey was to determine the extent of pain education in current Doctorate of Physical Therapy schools in the United States, including how pain is incorporated into the curriculum, the amount of time spent teaching about pain, and the resources used to teach about pain. The survey consisted of 10 questions in the following subject areas: basic science mechanisms and concepts about pain, pain assessment, pain management, and adequacy of pain curriculum. The overall response was 77% (167/216) for the first series of responses of the survey (Question 1), whereas 62% completed the entire survey (Questions 2-10). The average contact hours teaching about pain was 31 ± 1.8 (mean ± standard error of the mean) with a range of 5 to 115 hours. The majority of schools that responded covered the science of pain, assessment, and management. Less than 50% of respondents were aware of the Institute of Medicine report on pain or the International Association for the Study of Pain guidelines for physical therapy pain education. Only 61% of respondents believed that their students received adequate education in pain management. Thus, this survey demonstrated how pain education is incorporated into physical therapy schools and highlighted areas for improvement such as awareness of recent educational advancements. PERSPECTIVE: This article demonstrates how pain education is incorporated into physical therapy curricula within accredited programs. Understanding the current structure of pain education in health professional curriculum can serve as a basis to determine if recent publications of guidelines and competencies impact education.

Corticomotor excitability during a noxious stimulus before and after exercise in women with fibromyalgia.

The purposes of this study were to assess corticomotor excitability in people with fibromyalgia during a noxious stimulus before and after fatiguing exercise and examine associations with pain perception. Fifteen women with fibromyalgia completed three sessions: one familiarization and two experimental. The experimental sessions were randomized and involved measurement of pain perception and motor evoked potentials before and after (1) quiet rest and (2) isometric contraction of the elbow flexor muscles. Motor evoked potential amplitude of brachioradialis muscle was measured following transcranial magnetic stimulation delivered before, during, and after a noxious mechanical stimulus. After quiet rest, there was no change in pain perception. After the submaximal contraction, there was considerable variability in the pain response. Based on the changes in the experimental pain, subjects were divided into three groups (increase, decrease, and no change in pain). There was an interaction between pain response and the pain-induced change in motor evoked potentials. Those individuals who had an increase in motor evoked potentials during the pain test had an increase in pain after exercise. Thus, women with fibromyalgia were classified based on their pain response to exercise, and this response was associated with the change in corticomotor excitability during the application of a noxious stimulus.

Pain relief after isometric exercise is not task-dependent in older men and women.

INTRODUCTION: This study assessed the effect of isometric contractions that varied in intensity and duration on pain perception in adults older than 60 yr. METHODS: Pain perception was measured in 24 men and women (mean ± SD age = 72.2 ± 6.2 yr) using a pressure pain device applied to the right index finger before and after isometric contractions of the left elbow flexor muscles of the following doses: 1) three brief maximal voluntary contractions (MVC), 2) 25% MVC held for 2 min, and 3) 25% MVC held to task failure. RESULTS: Older adults reported increased pain thresholds (58 s vs 49 s, P < 0.001) and decreased pain ratings (2.8 vs 3.4, P < 0.001) after exercise, and these changes were similar across all three tasks (P = 0.94 and P = 0.55, respectively). Sex differences were identified with older women reporting greater pain sensitivity (lower pain thresholds [P = 0.01] and higher pain ratings [P = 0.004]) and larger reductions in pain ratings than men (23% vs 9%, P = 0.003) after isometric contractions. CONCLUSIONS: Older adults experienced similar reductions in pain after several different intensities and durations of isometric contractions. Both older men and women experienced increases in pain threshold, but only older women experienced reductions in pain ratings.

Pain perception after isometric exercise in women with fibromyalgia.

OBJECTIVE: The purpose of this study was to identify exercise protocols incorporating isometric contractions that provide pain relief in women with fibromyalgia. DESIGN: A before-after trial. SETTING: A physical therapy department in an academic setting. PARTICIPANTS: Fifteen women (mean ± SD, 52±11y) with fibromyalgia. INTERVENTIONS: Subjects completed 4 sessions: 1 familiarization and 3 experimental. The following randomized experimental sessions involved the performance of isometric contractions with the elbow flexor muscles that varied in intensity and duration: (1) 3 maximal voluntary contractions (MVCs), (2) 25% MVC held to task failure, and (3) 25% MVC held for 2 minutes. MAIN OUTCOME MEASURES: Experimental pain (pain threshold and pain rating), Fibromyalgia Impact Questionnaire, and fibromyalgia pain intensity (visual analog scale). RESULTS: After all 3 isometric contractions, there was considerable variability between subjects in the pain response. Based on the changes in experimental pain, subjects were divided into 3 groups (increase, decrease, no change in pain). Multiple regression analysis revealed that age, baseline experimental pain, and change in fibromyalgia pain intensity were significant predictors of the experimental pain response after the isometric contractions. CONCLUSIONS: We identified subgroups of women with fibromyalgia based on how they perceived pain after isometric contractions. The greatest pain relief for women with fibromyalgia occurred at a younger age and in women with the greatest experimental pain before exercise. Additionally, we established a link between experimental and clinical pain relief after the performance of isometric contractions.

Update on the relation between pain and movement: consequences for clinical practice.

It is generally thought that exercise is beneficial to alleviate pain. However, prolonged movement may lead to the development of painful injuries, because of the overload of low-threshold motor units. Especially in individuals with a pain condition, exercise prescription and the impact of fatigue is less clear. This may be because of the dual effects, aggravation and relief, which fatigue has on pain. The purpose of this review is to ascertain the relation between pain and the motor system, both in the development and management of pain. Recent studies show that fatigue alters pain-induced increases in corticomotor excitability and leads to within and between-muscle adaptations. Studies of acute pain have shown complex adaptations such as increased movement variability, which may be because of a search for motor solutions to prolong overall task performance. In contrast, chronic pain seems to limit movement duration, speed, and variability which could be protective in the short term but also counterproductive over time. Owing to these adaptations in movement strategies, pain chronicity may help to dictate exercise prescription. For example, the correct dosage of multimuscle, dynamic exercises would act to promote movement variability. Thus, it seems that exercise involving the use of different movement strategies could be effective in helping people to obtain exercise-induced benefits while avoiding injury and pain reaggravation.